Flying bird counts were carried out at Esperanza Bay (62°24'S, 56°59'W), Antarctic Peninsula, between November 1989 and February 1990. Six breeding species (Oceanites oceanicus, Chionis alba, Catharacta lonnbergi, Catharacta maccormicki, Larus dominicanus and Sterna vittata) and six visitor species (Macronectes giganteus, Fulmarus glacialoides, Daption capense, Pagodroma nivea, Fregetta tropica and Phalacrocorax atriceps) were recorded. Kelp gull and Antarctic tern populations have decreased in relation to the data by previous authors, perhaps as a result of the increased activity at Esperanza Station. Cygnus melanocoryphus was recorded for the first time at Esperanza Bay.

A serological study to detect antibodies against microbes in avian mycoplasmosis (Mycoplasma gallisepticum and M. synoviae), and salmonellosis (Salmonella gallinarum and S. pullorum) was carried out. A hundred and twelve Antarctic birds (42 Adelie penguins, Pygoscelis adeliae, 30 southern giant petrels, Macronectes giganteus and 40 skuas, Catharacta antarctica and C. maccormicki) from King George Island, the South Shetland Islands, and Laurie Island, the South Orkney Islands in Antarctica were studied. The serological test used in this study was a rapid agglutination test. According to the results and considering the number of samples analysed, it is reasonable to believe that Adelie penguins, southern giant petrels, and skuas populations of the areas mentioned above are free from mycoplasmosis and salmonellosis.